1. Field of the Invention
The present invention relates to a method and an apparatus for inspecting the surface of a semiconductor wafer or other body to be detected.
2. Related Art
A method and an apparatus in which defects inside a wafer is inspected by using dual-wavelength laser beam are publicly known. See Japanese Patent Unexamined Publications No. 11-354598, No. 11-237226, and Paper “Measuring technology of the size and the depth of surface defects on the entire wafer surface caused by two-wavelength beam scattering (OSDA: Optical Shallow Defect Analyzer)” written by Takeda Kazuo in Journal of Surface Science and Nanotechnology vol. 22, No. 5, pp. 323-331, 2001.
For example, internal measurement and surface measurement of a wafer are made possible by a wavelength difference between two wavelengths (difference between a short wavelength and a long wavelength).
SOI calibration cannot be performed by the surface inspection of a conventional dual-wavelength method. In addition, it has been impossible to quantitatively measure the information of interior interface of an SOI wafer.
Although foreign particle measurement on the surface of a thin film SOI wafer of the next generation can be performed by using a short wavelength (DUV), influence of a wafer base material cannot be quantitatively measured by the surface inspection of the conventional dual-wavelength method. For example, interface between a middle layer and a lower layer cannot be measured accurately. Particularly, small cavities or foreign particles inside a wafer cannot be accurately measured. This has caused an adverse effect in the yield of devices.